1. Field of the Invention
The present invention relates to the art of well completion methods and equipment for the production of hydrocarbon fluids. More particularly, the invention relates to methods and apparatus for downhole regulation of hydrocarbon fluid production rates.
2. Description of Related Art
Bottom hole well tools are exposed to extremely abrasive operating conditions. As hydrocarbon fluid is released from the naturally occurring in situ formation, sand, rock and other abrasive particles are drawn with it. In deeper wells where the in situ pressures are extremely high, the production pressure drop between the formation and the flow bore of the production tube is correspondingly high. Such high pressure differentials in the presence of a highly abrasive fluid rapidly erodes the production control tools. Fluid velocity through and over the tool surfaces, elements and apertures is an exponential function of the pressure differential drive. Hence, high pressure differentials translate to high fluid velocities. High velocity fluids entrained with abrasives translates to high rates of erosion, wear and failure.
Earth formation pressures and fluid production are not, however, fixed properties. Both of these properties change over time. Moreover, the changes are not necessarily linear or in predictable directions. The changes may be abrupt, irregular and/or fluctuating. In cases of an elongated production zone, often horizontal, the production properties may change in one section of the producing zone differently than those in another section of the same producing zone.
Although downhole tools for limiting the production rate of a production zone are known to the prior art, such tools have a fixed configuration. Production flow rate adjustments are usually made at the surface. Downhole flow rate adjustment is accomplished by removing the production tools from the well bore and replacing a first fixed flow rate tool with a second fixed flow rate tool of different capacity.
It is, therefore, an object of the present invention to provide active flow control, from the surface, over production from gravel pack installations through sand control screens down to an individual screen.
Another object of the invention is provision of means to regulate the inflow of fluids from a long, horizontal petroleum reservoir to maximize production.
Also an object of the present invention is provision of means to terminate production flow from a production screen or to divert flow from one screen to another within the screen assembly.
A further object of the invention is provision of means to adjust the production flow rate of a well.
These and other objects of the invention are served by a tool that is associated with a production sand screen to channel the screened production flow through a flow control zone. Within the flow control zone is a static flow control device that reduces the fluid pressure differential over an extended length of flow restrictive channel. At either end of the flow control device are transverse flow apertures disposed between the flow control zone and the internal flow bore of the primary production tube.
The apertures are flow controlled as either opened or closed completely. This operational set allows three flow states. When the apertures upstream of the flow control device are closed and those downstream are open, all production flow from the associated screen must pass through the flow control device. In doing so, the flow stream is required to follow a long, helical path. Traversal of the flow control device dissipates the pressure of state within the fluid thereby reducing the pressure differential across the production tool. The energy potential of the pressure is converted to heat.
When apertures upstream of the flow control device are open and those downstream are closed, production flow is shunted directly from the flow control zone into the internal flow bore of the primary production tube. This operational state permits the particular tool to run xe2x80x9copen chokexe2x80x9d but not necessarily all tools in the formation.
The third flow state closes both apertures to terminate all production flow from the associated screen.
A preferred embodiment of the invention provides a cylindrical tool mandrel within the internal bore of a production tube that forms an annular flow channel along the tube axis. Axially displaced from the screen inflow area, is a circumferential band of longitudinal stator columns that span radially across the flow channel annulus to funnel the annulus flow through gates between the stator columns. Further displaced axially along the flow channel annulus is a helically wound wall that also spans radially across the flow channel annulus. This helically wound wall is one embodiment of a static flow control device.
Two sets of flow apertures through the mandrel wall section link the annular flow channel with the internal bore of the production tube. A first aperture set is positioned axially displaced from the static flow control device opposite from the band of stator columns. A second aperture set is positioned axially displaced from the band of stator columns opposite from the flow control device. An axially slideable ring substantially encompasses the mandrel at an axial location adjacent to the stator columns opposite from the static flow control device. The ring is axially displaced by one or more hydraulic cylinders. From one annular edge of the ring projects a number of gate plugs. The number of plugs corresponds to the number of gates. The gate plugs overlie the second set of flow apertures at all positions of axial displacement but one.
At a first, axially stroked extreme position of the ring, the second flow aperture set is open to facilitate direct and unrestricted flow of production flow from the channel annulus into the internal bore.
At an intermediate axial position of the ring, the plugs close the gates between the stator columns thereby blocking flow to the first flow aperture set. Also at this intermediate setting, the gates block flow through the second set of apertures by their lapped, overlay location. Consequently, at the intermediate setting, no flow from the channel annulus is admitted into the inner bore.
At a second axial extreme position, the plugs are withdrawn from the gates to allow flow through the static flow control device and into the first set of flow apertures. Hoewever, at the second axial extreme position the plugs continue to block flow through the second set of flow apertures. Consequently, the flow stream is required to traverse the static flow control device to reach the inner production tube bore.